nix: strip ios library (#6503)

* strip ios like in android

* remove strip-unneeded in mac

* strip only simplex-chat libs

* flake.nix: strip only local symbols in MacOS library

* flake.nix: make libs writable

* flake.nix: better strip placement

* reduce framework size by exporting only public API symbols

apps/ios/SimpleX.xcodeproj/project.pbxproj

@@ -2319,6 +2319,9 @@
 				SWIFT_OPTIMIZATION_LEVEL = "-O";
 				SWIFT_VERSION = 5.0;
 				TARGETED_DEVICE_FAMILY = "1,2";
+				EXPORTED_SYMBOLS_FILE = "$(PROJECT_DIR)/SimpleXChat/exported_symbols.txt";
+				STRIP_INSTALLED_PRODUCT = YES;
+				STRIP_STYLE = "non-global";
 				VALIDATE_PRODUCT = YES;
 				VERSIONING_SYSTEM = "apple-generic";
 				VERSION_INFO_PREFIX = "";

apps/ios/SimpleXChat/exported_symbols.txt

@@ -0,0 +1,11 @@
+# Swift mangled symbols (Swift 5+ ABI stable prefix)
+_$s*
+
+# ObjC class/metaclass symbols (for NSObject subclasses)
+_OBJC_CLASS_$_*
+_OBJC_METACLASS_$_*
+
+# C API (SimpleX.h bridging header)
+_chat_*
+_haskell_init*
+_hs_init*

flake.nix

@@ -93,6 +93,7 @@
         for pkg in $out/_pkg/*.a; do
           chmod +w $pkg
           ${mac2ios.packages.${system}.mac2ios}/bin/mac2ios $pkg
+          [[ "$pkg" == *simplex-chat* ]] && ${pkgs.stdenv.cc.targetPrefix}strip -x $pkg
           chmod -w $pkg
         done